This invention relates to a method of controlling and regulating the startup operation of an internal combustion engine.
The startup operation of an internal combustion engine is critical with regard to maintaining the exhaust gas limit values. A rapid pressure buildup in the fuel supply and an early transition to pressure regulated operation are deciding factors here. German Patent DE 199 16 100 A1 describes a method for the startup of an internal combustion engine having a common rail injection system. On activation of the startup operation, a first mode is set. In the first mode, an attempt is made to increase the rail pressure as rapidly as possible. During startup, the rail pressure and/or the rotational speed of the internal combustion engine are compared with a limit value. As long as they remain beneath the limit value, the first mode remains set and the pressure is built up in the rail in a controlled fashion. If these values are above the limit value, a second mode is set. In the second mode the regulation of the rail pressure is activated. However, the rail pressure may drop below the limit value again due to the injected fuel. Therefore, the first mode is set again. Thereafter, if the rail pressure again exceeds the limit value, the system switches back to the second mode. This change in modes is problematical because it causes pressure fluctuations during the startup operation.
The object of this invention is to make the startup operation more reliable.
This object is achieved by a method of controlling and regulating the startup operation in which the first time the second mode is set, it is retained for the remaining startup operation. The rail pressure is thus regulated even when it again falls below a limit value, e.g., a regulator enable pressure. The regulator enable pressure is understood to be the pressure at which the high-pressure regulation is enabled. In the first mode, a control signal for a pressure control means, in particular an intake throttle, is calculated in a form such that full delivery of fuel is ensured. An adjustment of the control signal is achieved when it is determined as a function of the engine rotational speed. Emergency operation is activated in the event of a failure of the rail pressure sensor. When emergency operation is activated, the engine rotational speed is used as the authoritative characteristic parameter for the startup operation.
This invention offers the advantage that a stable steady state of the overall system is achieved at an earlier point in time. For implementation of the function, no additional sensor signals or output signals for final control elements are necessary, so that they can be applied with little effort.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.